The Influence of Frequency Containment Reserve Flexibilization on the Economics of Electric Vehicle Fleet Operation

Simultaneously with the transformation in the energy system, the spot and ancillary service markets for electricity have become increasingly flexible with shorter service periods and lower minimum powers. This flexibility has made the fastest form of frequency regulation - the frequency containment reserve (FCR) - particularly attractive for large-scale battery storage systems (BSSs) and led to a market growth of these systems. However, this growth resulted in high competition and consequently falling FCR prices, making the FCR market increasingly unattractive to large-scale BSSs. In the context of multi-use concepts, this market may be interesting especially for a pool of electric vehicles (EVs), which can generate additional revenue during their idle times. In this paper, multi-year measurement data of 22 commercial EVs are used for the development of a simulation model for marketing FCR. In addition, logbooks of more than 460 vehicles of different economic sectors are evaluated. Based on the simulations, the effects of flexibilization on the marketing of a pool of EVs are analyzed for the example of the German FCR market design, which is valid for many countries in Europe. It is shown that depending on the sector, especially the recently made changes of service periods from one week to one day and from one day to four hours generate the largest increase in available pool power. Further reductions in service periods, on the other hand, offer only a small advantage, as the idle times are often longer than the short service periods. In principle, increasing flexibility overcompensates for falling FCR prices and leads to higher revenues, even if this does not apply across all sectors examined. A pool of 1,000 EVs could theoretically generate revenues of about 5,000 EUR - 8,000 EUR per week on the German FCR market in 2020.Comment: Preprint, 23 pages, 21 figures, 10 table

Evaluation of the Effects of Smart Charging Strategies and Frequency Restoration Reserves Market Participation of an Electric Vehicle

The emergence of electric vehicles offers the opportunity to decarbonize the transportation and mobility sector. With smart charging strategies and the use of electricity generated from renewable sources, electric vehicle owners can reduce their electricity bill as well as reduce their carbon footprint. We investigated smart charging strategies for electric vehicle charging at household and workplace sites with photovoltaic systems. Furthermore, we investigated the participation of an electric vehicle in the provision of positive automatic frequency restoration reserve (aFRR) in Germany from 30 October 2018 to 31 July 2019. We find that the provision of positive aFRR in Germany returns a positive net return. The positive net return is, however, not sufficient to cover the current investment cost for a necessary control unit. For home charging, we find that self-sufficiency rates of up to 48.1% and an electricity cost reduction of 17.6% for one year can be reached with unidirectional smart charging strategies. With bidirectional strategies, self-sufficiency rates of up to 56.7% for home charging and electricity cost reductions of up to 26.1% are reached. We also find that electric vehicle (EV) owners who can charge at their workplace can reduce their electricity cost further. The impact of smart charging strategies on battery aging is also discussed.Peer ReviewedPostprint (published version

Self-sufficiency and charger constraints of prosumer households with vehicle-to-home strategies

In recent years, the market of electric vehicles has been growing strongly. This growth is accompanied bydiscussions on vehicle-to-home strategies that allow households with a photovoltaic system and an electricvehicle both to charge the vehicle with solar energy and to supply energy from the vehicle to the household.However, vehicle-to-home technology is still not yet widely implemented in prosumer households and thereis still little literature about the impact of technological constraints given by the hardware and chargingprotocols on prosumer energy consumption. To close this research gap, we develop heuristic vehicle-to-homecharging strategies that aim to increase self-sufficiency, vehicle availability and traction battery lifetime. Wediscuss charging power constraints due to technical limitations measured in the laboratory and communicationprotocols. We investigate the impact of charging power constraints, bidirectional charger capability andforecasting algorithms on the self-sufficiency of the prosumer household. The simulation model integrates acomprehensive electric vehicle model, photovoltaic system model and historic measurement data of prosumerand driving profiles. We propose and simulate three different exemplary mobility profile scenarios. Themobility scenarios differ in their departure and arrival time distributions and are named Worker, Half-timeWorker and Late Worker. The developed smart charging strategies can increase the self-sufficiency of thehousehold by up to 16.9 percentage points in comparison to charging the vehicle with maximum power uponplug-in. Decreasing the minimum charging power constraint from 4.1 kW to 1.8 kW can increase self-sufficiencyby up to 10.5 percentage points. Smart charging strategies, the use of a bidirectional charger, relaxation ofcharging power constraints and the use of forecasting algorithms increase the self-sufficiency of a prosumerhousehold with a photovoltaic system and an electric vehicle

A Comprehensive Electric Vehicle Model for Vehicle-to-Grid Strategy Development

A comprehensive electric vehicle model is developed to characterize the behavior of the Smart e.d. (2013) while driving, charging and providing vehicle-to-grid services. To facilitate vehicle-to-grid strategy development, the EV model is completed with the measurement of the on-board charger efficiency and the charging control behavior upon external set-point request via IEC 61851-1. The battery model is an electro-thermal model with a dual polarization equivalent circuit electrical model coupled with a lumped thermal model with active liquid cooling. The aging trend of the EV’s 50 Ah large format pouch cell with NMC chemistry is evaluated via accelerated aging tests in the laboratory. Performance of the model is validated using laboratory pack tests, charging and driving field data. The RMSE of the cell voltage was between 18.49 mV and 67.17 mV per cell for the validation profiles. Cells stored at 100% SOC and 40 °C reached end-of-life (80% of initial capacity) after 431–589 days. The end-of-life for a cell cycled with 80% DOD around an SOC of 50% is reached after 3634 equivalent full cycles which equates to a driving distance of over 420,000 km. The full parameter set of the model is provided to serve as a resource for vehicle-to-grid strategy development